Learning Parshas Haazinu by heart:
There is an old tradition of memorizing the Song of Haazinu. The verse states “And now you shall write this song [of Haazinu] and you shall teach it to Bnei Yisrael; place it in their mouths [memorize it].” From here we learn that the Jewish people in the times of Moshe were commanded to learn this song by heart. The Maharal of Prague stated that one is to recite the Parsha of Haazinu by heart each day and that doing so brings success and long life. The Baal Shem Tov directed Rav Chaim Rappaport of Levov to recite the song of Haazinu by heart during his famous journey. The Maggid of Mezritch stated that the song of Haazinu is to be memorized [by the masses]. The Rebbe Rayatz stated “I heard from Gedolim that every Jew is required to know the song of Haazinu by heart. If the businessmen only knew of the great blessing that the recital of Haazinu from memory can bring to their business, they would be a lot more careful in this.”
 This tradition is not recorded in any classical sources of previous times [other than the verse mentioned above and the Sichos below which record it in the name of the Maharl and the Maggid of Mezritch] and was seemingly an oral tradition. Many schools have a tradition of learning it by heart. Vetzrauch Iyun Gadol as to why the Poskim or Mefarshim on the verse ibid make no mention of this tradition for the generations after. See footnotes below.
 Vayeilech 31/19
 Rashi ibid
 Even Ezra ibid; Rasag ibid
 Seemingly however, this command only applies to that generation, and hence we do not find that every Jew ia taught Haazinu by heart, and it is simply viewed as a good Segula. Furtehrmore, perhaps one can say that the command was only on Moshe to teach it to them until they memorize it and it was not a command on the Jewish people even in that generation to learn it, and certainly not in later generations, although its Segula still remains. Vetzaruch Iyun..
 Sefer Hazichronos 1/29
 Sefer Hazichronos 1/139 [English]
 Sefer Hasichos 1944 p. 136-138; Sefer Hatoldos Hamaharash [of Rebbe] p. 74
 Sefer Hasichos 1941 p. 46 [Hebrew]